1. Field of the Invention
The present invention relates to a rotary-cup liquid supply device for supplying a solution, such as a solution of a silicon compound dissolved in an organic solvent, to form a film such as a SOG (Spin-on-Glass) coating film on a surface of a planar workpiece such as a glass substrate.
2. Description of Relevant Art
There has heretofore been known a rotary-cup liquid supply device having an outer cup, an inner cup rotatable by a spinner, the inner cup being disposed in the outer cup, and a flow-rectifying plate attached to the lower surface of a lid which closes an upper opening of the inner cup, in confronting relation to the surface of a planar workpiece set in the inner cup.
Japanese laid-open patent publication No. 6-170315 discloses an improvement in the above conventional rotary-cup liquid supply device. In the improved device, an annular spacer is mounted on an inner bottom surface of the inner cup, defining a small space between the annular spacer and the flow-rectifying plate in surrounding relation to the planar workpiece. The annular spacer has holes defined therein which serve as both air vent holes and drain holes. In operation, the inner cup is rotated with the planar workpiece set therein being surrounded by the small space, and a coating solution applied to the planar workpiece is spread over the surface thereof by centrifugal forces. Since turbulent flows and pressure fluctuations are minimized in the small space, the applied coating solution is uniformly coated on the surface of the planar workpiece. However, the annular spacer cannot easily be cleaned or otherwise serviced for maintenance because of the holes defined therein which serves as both air vent holes and drain holes.